Within the powder metallurgical field, copper and nickel has since long been used as alloying elements in the production of high strength sintered components.
Sintered iron-based components can be produced by mixing alloying elements with iron based powders. However, this may cause problems with dust and segregation which may lead to variations in size and mechanical properties of the sintered component. As for nickel powder used in powder metallurgy the absence of “dusting” is of outmost importance as nickel dust is hazardous and creates a work environmental problem. In order to avoid segregation the alloying elements may be pre-alloyed or diffusion alloyed with the iron powder. In one method the iron powder is diffusion alloyed with copper and nickel for production of sintered components from iron-based powder compositions containing nickel and copper.
WO 2006/083206 relates to a powder metallurgical combination comprising an iron-based powder A essentially consisting of core particles of iron pre-alloyed with Mo and having 6-15% by weight of copper diffusion alloyed to the core particles, an iron-based powder B essentially consisting of particles of iron pre-alloyed with Mo and having 4.5-8% by weight of Ni diffusion alloyed to the core particles, and an iron-based powder C essentially consisting of particles of iron pre-alloyed with Mo. The invention of this document does not relate to powders not comprising Mo or powder mixtures containing pure iron-powder.
UK patent application GB 2 431 166 relates to making a wear resistant member by compacting a powder mixture containing a matrix forming powder and a hard phase forming powder. The matrix forming powder containing 90 mass % or more of particles having a maximum diameter of 46 μm, and the hard phase forming powder being 40 to 70 mass % with respect to the powder mixture; and a mixture of the two powders are compacted powder and sintered. The hard phase forming powder can consist of 20-60 wt % Mo 3-12 wt % Cr, 1-12 wt % Si and the balance Co and inevitable impurities. The matrix forming powder can be obtained by using one of the powders A-E (page 19-20). None of the powders A-E comprise a pure iron.
US 2001/0028859 provides an iron-based powder composition for powder metallurgy having excellent flowability at room temperature and a warm compaction temperature, having improved compactibility enabling lowering ejection force in compaction. The iron-based powder composition comprises an iron-based powder, a lubricant, and an alloying powder. None of the embodiments illustrate the use of pure iron powder combined with a diffusion alloyed iron-based powder.
It is however obvious that, when producing a sintered iron-based component, from a powder wherein copper and nickel are diffusion alloyed, the content of the alloying elements in the sintered iron-based component will be substantially identical with the content of alloying elements in the used diffusion alloyed powder, and that in order to reach different contents of the alloying elements in the sintered component yielding different properties, iron-based powders having different contents of the alloying elements have to be used.
A problem is, among other things, that a specific powder is required for each desired chemical composition of a sintered iron-based component having alloying elements from e.g. nickel, or nickel in combination with copper. Another problem is to assure proper mechanical properties of such a sintered iron-based component having alloying elements from nickel, or nickel in combination with copper component and combined with pure iron powder.